With development of advanced technology, a power supply voltage level is designed to become smaller and smaller. For example, a power supply voltage level may be designed to become a slightly higher than a threshold voltage of a transistor component. Such smaller voltage supply level introduces a problem that it is difficult to design a low dropout voltage regulator. In addition, another problem may be that the efficiency of a low dropout voltage regulator may become worse. It is difficult to design a low dropout voltage regulator with high power supply rejection capability.